If the rectangular guiding curve equals the total diameter, it is a waste of material and the waveguide will dominate the baffle. Overall production is more expensive and mounting tedious. If the rectangular guiding curve was the size of the cut sides, termination is unnecessarliy lost for a huge total area.
I printed a 1" scaled version of the 4 fane plug on my 0.2mm nozzle and tested it against a similar size horn.
Blue is a straight up axisymmetric OSSE, red is the throat plug cousin.
The secondary curves are THD plots
It's interesting to see how the plug gracefully deals with the breakup at 18.5kHz and improves loading and thd in the 700hz region
As a side note I have to meantion that there was a bit of stringing on the phase plug print (which might act like dr. Geddes' foam)
Attachments
Those are interesting results. I suspect that the throat acoustic impedance has a large peak around 700 Hz and gets quite low above that (which would indicate quite a strong reflection at the plug/wg interface), otherwise I have no explanation for the behaviour shown. With four vanes I wouldn't expect such clean response at high frequencies, you obviously managed to print the walls thin enough. Great contribution!
Did you have a chance to measure directivities?
Did you have a chance to measure directivities?
Make sure you select the 'curve in x-graph' as the reference mode, with the degree marker set to zero. Luckily, I already have this in my clipboard from posting in another thread
Thanks, that seems to work marvelously at HF. I would be especially interested in a comparison with a 1" throat without the plug.
There's some reflection at 1.2 ms but probably it doesn't affect the results too much.
- BTW, I'm writing an App Note and I've already devised a name for the device: ESP (External Shaping Plug)
Mabat,
another question. I am considering to slightly limit the vertical dimensions of the waveguide and make it elliptical. This i due to available baffle space. I use the typical -X*sin(p)^2 modifier.
Is it possible to still enforce a determinate outside shape to the waveguide? This question stems from the question of replaceability. A circular waveguide has an outside diameter and that is it. It can easily be exchanged, if one learns about flaws. It has a standard shape. Can I do something like this when I make the waveguide symmetrical on two axes, too?
another question. I am considering to slightly limit the vertical dimensions of the waveguide and make it elliptical. This i due to available baffle space. I use the typical -X*sin(p)^2 modifier.
Is it possible to still enforce a determinate outside shape to the waveguide? This question stems from the question of replaceability. A circular waveguide has an outside diameter and that is it. It can easily be exchanged, if one learns about flaws. It has a standard shape. Can I do something like this when I make the waveguide symmetrical on two axes, too?